Method of processing swelling coals for use in by-product ovens



Patented Feb. 15, 1944 zsiissi i ESSING SWELLING GOALS FEE HEB EN BY=IPRODUCT OVENS Waiter M. Fuchs, State College, Pa.

No Drawing.

The invention relates to a processed coking Application December 17. 1941, Serial No. 429,336 l 2 Claims. (oi. 202-25 coal andto a method of decreasing the swelling pressure of coals.

One 01' the objects of my invention is to prepare a swelling coal for safe use in the manufacture g of coke in byproduct ovens.

Another object 01' my invention is to treat a swelling coal with air of controlled moisture content in order to decrease its swelling power without impairing its coking quality.

Another object o! my invention is to oxidize a relatively low temperature and pressure, as a pretreatmentto coking, swelling coals of the size distribution used for 'composing carbonization blends.

Anhther object or my invention is to use pretion is intended to generally explain the same without limiting the same in any manner.

Lih I do not wish to be limited to the specific examples which are later given herein as illustrating ents of the invention, since sea, in may be e without depart from the spirit oi the invention.

The term swelling pressure of coal is used to indicate the fact that pressure against the oven wall is noted during carbonizntion. it has been recounined that swelling power, 1. e., the property to develop swelling pressure, is common to all coking coals. At pint, the term swelling coals is used for a group of coking coals which belong to the lowand medium-volatile group, on

hibit a low or medium cnheobility, and are found,

Control oi swelling pressure has been greatly incilitnted by n therm emit analysis of the phenomenon (J. Franklin inst. 231, its-lit, will and hy the develoent oi a satisfactory measun ing device (hm. fies on, Meeting, may 1941;

New York city), e measuring device permits towort; with a coking ember oi variable width; the data obtained one be extrapolated to actual conditions.

tit

it been established t the swelling power can deored by weathering, addition or inert material, oi chibnis (either organic or inorganic), and the like. All these actions may be successful as far as mere decrease of swelling power is concerned. They result, however, as a rule in a simultaneous deterioration of quality of either coal or coke or both.

The same is noted upon-treating coal with air, as suggested in various patents for diverse purposes. In U. S. Patent 1,993,198 (Wisner) it is stated that finely crushed volatile coal in the range of 350 to 450" F. is in a rascent condition as regards oxygen, that is, it is use to be rapidly modified and conditioned for coking in ovens and carbonizing in retorts, for stopping sticking to container walls, and controlling expansion during the softening period of carbonization, for producing a denser and stronger product, and for shortening the process cycle, thereby contributing a new stepto carbonization technology. To carry out the process, finely divided coal freed of surface moisture is treated for a time from 10 to minutes with an amount of air varying from zero to 2000 cubic feet per ton of coal.

It is correct that under the conditions disclosed by Wisner a rapid modification of the coal occurs. But because of this rapidity of change the process is not applicable to swelling coals which do not posses a high calreability and quickly loose their value as coking coals by such treatment. This is demonstrated by the following observations:

A swelling coal with 13% vol. matter ground to pass a mesh sieve was treated at various temperatures for various lengths of time in a rotary furnace with a current of airi The effect or the treatment was followed by nieasuremen s of swelling pressure and by core button tests. irom 150 0. upward the swelling power decreased uuickly. This, however, was accompanied by a rapid deterioration oi coal quality. Colic buttons prepared at even intervals showed a steady decrease in strength... After a relatively short time. e. n, minutes at 200 Gno coho button at all was termed, merely an incoherent residue was obtamed. Hence, the Wiener process applied to lowand medium-volatile coals results in e serious deterioration defeating the purest dei =2 the swelling power without impairing the coke iorg properties.

In U. S. Patent 2,lt7,lilil (Benezeoh) an improvement or coiring coal is claimed by subjecting it to a predeteed limited degree oi oxidation to reduce its esbility. The process is carried outhy storing the coal with only the air normally entred in it, and aging the coal in 2 the bunker column for at least several days at a temperature from 130 to 160 C.

I have designed a process in order to decrease the swelling pressure of swelling coals by treatment with air, and yet avoid both the danger of deterioration attendant upon rapid oxidation, and the inconvenience inherent to an agin M00888 extended over a period of several days. The process is based on the following observations:

1. In contrast to finely crushed swelling coal, swelling coal of commercial size distribution, e. g., inch slack, is not easily oxidized. A slack sample of coal with 18% volatile matter was studied under the conditions recorded for the 60 mesh sample. As shown by coke button tests, the coking properties were hardly impaired even after 10 hours of oxidation. Blends prepared'by the use of oxidized slack samples showed a substantial decrease of swelling pressure, e. g., from 5 lbs. to 1.5 lbs. per square inch. However, difliculties were encountered in attempts to duplicate results closely.

2. Satisfactory duplicability of results, satisfactory diminutions of swelling power, and unchanged or even improved coking properties resulted from a treatment with air of constant humidity. Apparently, this factor has escaped attention in the prior art.

3. Optimum conditions .of processing were determined by following the operation with the measuring device.

The application of these observations is illustrated by the following examples:

Example 1.-A --V inch slack sample of a Pocahontas coal with 16.3% volatile matter was treated in a rotary furnace at 300 C. for three hours with a current of air that had been saturated with water vapor at room temperature; per ton of coal, 8300 cubic feet of air were used. The showed a substantial decrease oi swelling pressure and permitted obtainingofacokewith decreased porosityand increasedstrensth.

trample 2.--A inch slack sample of a Millerseamcoalwith 22.0% volatile matter was treated in a rotary furnace at 240' C. for one hour with a current of air thatflhad.'been saturated with water vapor at 60 0.; per ton of coal, 1100 cubic feet of air were used. The

processed coal showed a substantial decrease of swelling pressure without a noticeable decrease of cakeability.

. I claim:

1. A method of processing swelling coals of commercial size distribution for use in byproduct ovens by treatment with air of. a moisture content between 0.01 and 0.5 lb. of water vapor per lb. of dry air. the treatment to be effected prior to carbonization in the temperature range from 150' C. to 300 C. for such a period of time that the original swelling pressure is decreased to a value not exceeding 1.5 lb. per square inch of oven wall on the basis of the coal charge to be 5 carbonized.

2. A method of processing swelling coals of commercial size distribution for use in byproduct ovens by treatment with air of a moisture content between 0.01 and 0.5 lb. of water vapor per 1b. of dry air maintained by saturating the air period of time that the original swelling pressure is decreased to a value not exceeding 1.5 lb. per square inch of oven wall on the basis of the coal charge to be carbonized.

WALTER M. FUCHS. 

